Classifications

• • C—CHEMISTRY; METALLURGY
  • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
  • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
  • C02F1/00—Treatment of water, waste water, or sewage
  • C02F1/46—Treatment of water, waste water, or sewage by electrochemical methods
  • C02F1/461—Treatment of water, waste water, or sewage by electrochemical methods by electrolysis
  • C02F1/463—Treatment of water, waste water, or sewage by electrochemical methods by electrolysis by electrocoagulation
• • C—CHEMISTRY; METALLURGY
  • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
  • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
  • C02F1/00—Treatment of water, waste water, or sewage
  • C02F1/46—Treatment of water, waste water, or sewage by electrochemical methods
  • C02F1/461—Treatment of water, waste water, or sewage by electrochemical methods by electrolysis
  • C02F1/46104—Devices therefor; Their operating or servicing
  • C02F1/46109—Electrodes
  • C02F1/46114—Electrodes in particulate form or with conductive and/or non conductive particles between them
• • C—CHEMISTRY; METALLURGY
  • C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
  • C23F—NON-MECHANICAL REMOVAL OF METALLIC MATERIAL FROM SURFACE; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL; MULTI-STEP PROCESSES FOR SURFACE TREATMENT OF METALLIC MATERIAL INVOLVING AT LEAST ONE PROCESS PROVIDED FOR IN CLASS C23 AND AT LEAST ONE PROCESS COVERED BY SUBCLASS C21D OR C22F OR CLASS C25
  • C23F13/00—Inhibiting corrosion of metals by anodic or cathodic protection
  • C23F13/02—Inhibiting corrosion of metals by anodic or cathodic protection cathodic; Selection of conditions, parameters or procedures for cathodic protection, e.g. of electrical conditions
• • C—CHEMISTRY; METALLURGY
  • C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
  • C23F—NON-MECHANICAL REMOVAL OF METALLIC MATERIAL FROM SURFACE; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL; MULTI-STEP PROCESSES FOR SURFACE TREATMENT OF METALLIC MATERIAL INVOLVING AT LEAST ONE PROCESS PROVIDED FOR IN CLASS C23 AND AT LEAST ONE PROCESS COVERED BY SUBCLASS C21D OR C22F OR CLASS C25
  • C23F13/00—Inhibiting corrosion of metals by anodic or cathodic protection
  • C23F13/02—Inhibiting corrosion of metals by anodic or cathodic protection cathodic; Selection of conditions, parameters or procedures for cathodic protection, e.g. of electrical conditions
  • C23F13/04—Controlling or regulating desired parameters
• • C—CHEMISTRY; METALLURGY
  • C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
  • C23F—NON-MECHANICAL REMOVAL OF METALLIC MATERIAL FROM SURFACE; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL; MULTI-STEP PROCESSES FOR SURFACE TREATMENT OF METALLIC MATERIAL INVOLVING AT LEAST ONE PROCESS PROVIDED FOR IN CLASS C23 AND AT LEAST ONE PROCESS COVERED BY SUBCLASS C21D OR C22F OR CLASS C25
  • C23F13/00—Inhibiting corrosion of metals by anodic or cathodic protection
  • C23F13/02—Inhibiting corrosion of metals by anodic or cathodic protection cathodic; Selection of conditions, parameters or procedures for cathodic protection, e.g. of electrical conditions
  • C23F13/06—Constructional parts, or assemblies of cathodic-protection apparatus
• • C—CHEMISTRY; METALLURGY
  • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
  • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
  • C02F1/00—Treatment of water, waste water, or sewage
  • C02F1/46—Treatment of water, waste water, or sewage by electrochemical methods
  • C02F1/461—Treatment of water, waste water, or sewage by electrochemical methods by electrolysis
  • C02F1/46104—Devices therefor; Their operating or servicing
  • C02F1/46109—Electrodes
  • C02F2001/46133—Electrodes characterised by the material
• • C—CHEMISTRY; METALLURGY
  • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
  • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
  • C02F2201/00—Apparatus for treatment of water, waste water or sewage
  • C02F2201/46—Apparatus for electrochemical processes
  • C02F2201/461—Electrolysis apparatus
  • C02F2201/46105—Details relating to the electrolytic devices
  • C02F2201/4612—Controlling or monitoring
• • C—CHEMISTRY; METALLURGY
  • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
  • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
  • C02F2303/00—Specific treatment goals
  • C02F2303/08—Corrosion inhibition
• • C—CHEMISTRY; METALLURGY
  • C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
  • C23F—NON-MECHANICAL REMOVAL OF METALLIC MATERIAL FROM SURFACE; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL; MULTI-STEP PROCESSES FOR SURFACE TREATMENT OF METALLIC MATERIAL INVOLVING AT LEAST ONE PROCESS PROVIDED FOR IN CLASS C23 AND AT LEAST ONE PROCESS COVERED BY SUBCLASS C21D OR C22F OR CLASS C25
  • C23F2213/00—Aspects of inhibiting corrosion of metals by anodic or cathodic protection
  • C23F2213/30—Anodic or cathodic protection specially adapted for a specific object

Definitions

• the present invention relates to an electrochemical apparatus and, in particular, an electrocoagulation unit for removing contaminants from a liquid.
• Contaminants include metal ions, such as arsenic, chromium, copper, cadmium, nickel, lead and zinc; suspended solids, such as silt and clay; organic compounds, such as hydrocarbons; and salts, such as phosphates.
• a contaminated liquid may be treated with a coagulating agent, which reacts with the contaminants to form insoluble compounds that aggregate or flocculate to form larger particles. These larger particles can then be
• contaminants can also be removed from liquids by electrocoagulation.
• Electrocoagulation is similar to chemical coagulation in that it relies on the reaction between a coagulating agent and the contaminants to form insoluble compounds, which aggregate or flocculate to form larger particles.
• a potential is applied across a cathode (herein the working cathode or WCAT) and an anode (herein the working anode or WAN) to induce the corrosion of the WAN in the liquid under treatment.
• WCAT working cathode
• WAN anode
• the WAN dissolves in the liquid, thereby releasing ions which act as the coagulating agent.
• the rate of corrosion and, hence, the rate of dosing can be controlled by varying the current through the electrodes.
• electrocoagulation relies on the electrode corroding or dissolving into the liquid under treatment.
• the corrosion of the electrode is essential to contaminant removal, as coagulation and flocculation cannot occur unless corrosion takes place.
• the electrodes of an electrocoagulation unit therefore, require regular replacement and this adds to the cost of the overall process. It is among the objects of embodiments of the present
• an electrochemical apparatus comprising:
• the apparatus further comprises a protective electrode (ProElect) , said protective electrode being
• a source of direct current such that electron flow takes place from the protective electrode (ProElect ) to the cathode (WCAT) and/or anode (WAN) in the chamber, said protective electrode (ProElect ) being formed from a different material to the cathode (WCAT) or anode (WAN) in the chamber.
• WCAT and anode (WAN) in the chamber, thereby causing the consumable surface of the anode (WAN) to dissolve in the liquid;
• the protective electrode (ProElect ) acts as the positive electrode (Protective Anode - ProAn)
• the cathode (WCAT) and anode (WAN) of the electrochemical chamber act as the negative electrode (Protective cathode - ProCat) of the
• This negative electrode (ProCat) is protected from corrosion by the impressed current, which reduces the negative electrode's susceptibility to oxidation.
• the effect is known as cathodic protection and is particularly important when the electrochemical apparatus is out of use, and no potential difference is applied across the anode (WAN) and cathode (WCAT) to deliberately effect corrosion of the anode (WAN) .
• the anode (WAN) and cathode (WCAT) of the electrochemical cell may be susceptible to natural corrosion, particularly if the liquid in the chamber contains contaminants that aid the corrosive process. This is undesirable, as it can lead to degradation of the electrode (s) without the benefit of e.g. effective
• the present invention can be used to reduce the risk of corrosion of the anode (WAN) and cathode (WCAT) particularly during such out-of-use periods, thereby increasing the longevity of the electrode (s) and the cost- effectiveness of e.g. the overall electrocoagulation process.
• WAN anode
• WCAT cathode
• the protective electrode can also be used to protect the cathode (WCAT) and anode (WAN) of the electrochemical cell without compromising the ability of the anode (WAN) to corrode or dissolve upon application of a potential difference across the cathode (WCAT) and anode (WAN) of the electrochemical cell.
• the apparatus of the present invention is preferably an electrocoagulation unit, whereby, upon application of a
• the electrochemical apparatus comprises an electrochemical chamber.
• the chamber comprises an inlet through which liquid requiring treatment is introduced.
• the chamber may also include an outlet for the removal of liquid following treatment.
• liquid is passed through the chamber in a substantially continuous process .
• An anode (WAN) and cathode (WCAT) are disposed within the electrochemical chamber.
• the anode (WAN) and cathode (WCAT) are distinct structural elements.
• the anode and cathode may take the form of separate plates or rods that extend into the liquid contained in the electrochemical chamber.
• the anode (WAN) comprises a consumable surface, which, upon application of a potential difference across the anode (WAN) and cathode (WCAT) , dissolves in the liquid.
• the dissolved anode material acts as a coagulating agent.
• the coagulating agent preferably reacts with contaminants in the liquid to form insoluble compounds that aggregate or
• a group of cathodes e.g. series of plates
• a group of anodes e.g. series of plates
• the group of cathodes and group of anodes may be connectable to each other via a single source of direct current. Alternatively, multiple sources of direct current may be used.
• the cathode (s) and anode (s) of the electrochemical cell may be formed of any suitable material.
• the anode (s) and/or the cathode (s) may comprise of at least one of the following: aluminium, iron, steel, stainless steel, copper, graphite, reticulated vitreous carbon and a
• the cathode(s) and anode (s) may be formed of the same material.
• both the cathode (s) and anode (s) may be formed of aluminium, steel and/or iron.
• the cathode (s) and anode (s) may be formed of different materials.
• the cathode (s) comprises iron (e.g. steel) which in this instance serves as a pseudo-dimensionally stable material, while the anode (s) from which the floe is generated comprises aluminium.
• aluminium/aluminium aluminium/aluminium, iron/dimensionally stable electrode and aluminium/dimensionally stable electrode.
• the apparatus may include a source of direct current that can be used to pass a direct current between the cathode (s) (WCAT) and anode (s) (WAN) in the electrochemical chamber.
• WCAT cathode
• WAN anode
• the apparatus further comprises a
• the protective electrode (ProElect ) and a source of direct current.
• the protective electrode (ProElect ) may be connected to the cathode (s) (WCAT) and/or anode (s) (WAN) in the chamber via the source of direct current, such that electron flow takes place from the protective electrode (ProElect)to the cathode (s)
• electrons protects the cathode (s) (WCAT) and/or anode (s) (WAN) in the chamber from corrosion.
• WCAT cathode
• WAN cathode
• WCAT cathode
• both the cathode (s) and the anode (s) in the chamber are protected from corrosion.
• the apparatus may comprise a first protective electrode (s) for connection to the cathode (s) in the chamber, and a second protective electrode (s) for connection to the anode (s) in the chamber.
• the anode (s) and cathode (s) are coupled to the same protective electrode (s) .
• the cathode (s) and/or anode (s) in the chamber may be over-protected by passing a relatively large current between the cathode (s) /anode (s) and their protective electrodes (s) . Over protection occurs when the impressed
• the electrochemical apparatus may include a gas collector for collecting any gas (e.g. hydrogen) produced in the
• Any suitable current may be passed between the protective electrode (s) and the cathode (s) (WCAT) or anode (s) (WAN) of the electrochemical chamber such that the system is maintained below its characteristic corrosion potential ( E cor r ) such that a negligible rate of electrode corrosion is achieved.
• Typical values range from 7 to 23mA (approximately 6-20 ⁇ / ⁇ 2 ) on the size of system presented in the example. These values will be dependant on the electrode material being protected and the liquid in contact with the electrodes.
• electrode surface potential to within the range of + 25mV from the protection potential, more preferably within the range of 0 and -25mV of the protection potential.
• mitigation the current density preferably is from 10 to 200 mA/m 2 , more preferably from 30 to 200 mA/m 2 , even more
• the preferred protection potential depends on the characteristics of the electrode pack (e.g. size, material, gap) and liquid (e.g. pH, conductivity, temperature) , therefore requiring defining for each system.
• the protective electrode (s) (ProElect) may be formed of any suitable material.
• the protective electrode (s) (ProElect) is formed from a different material to the anode (s) and/or cathode (s) in the chamber.
• the protective electrode (s) is formed of a noble metal, such as platinum, or any commercially available dimensionally stable electrode (e.g titanium coated electrodes, lead dioxide and diamond coated electrodes) .
• Groups of protective electrodes e.g. series of plates may be employed. These may be coupled to the cathode (s) and/or anode (s) via one or more sources of direct current. The one or more sources of direct current may form part of the electrochemical apparatus.
• the protective electrode is present in the same chamber in liquid contact, directly or via a liquid bridge, with the anode (s) (WAN) and cathode (s) (WCAT) . Any suitable current may be passed between the cathode (s)
• Typical values range from 1 to 10A (0.5-5mA/cm 2 ) for the size of system presented in the example.
• the electrochemical apparatus and, in particular, the
• electrocoagulation unit may be used to treat any liquid that can function as an electrolyte for the electrochemical
• Suitable liquids include aqueous solutions, such as seawater, brackish water, river water and lake water.
• the liquid may also be a waste water stream, such as an industrial, agricultural or domestic waste water stream.
• the electrochemical apparatus and, in particular, the
• electrocoagulation unit may be used for the removal of any suitable species, such as dissolved ions and/or organic
• the electrochemical apparatus and, in particular, the electrocoagulation unit may be used to remove inorganic anions, such as phosphate and/or metal ions, such as nickel and heavy metal ions (Hg, Cr and Pb) from the liquid under treatment.
• inorganic anions such as phosphate and/or metal ions, such as nickel and heavy metal ions (Hg, Cr and Pb) from the liquid under treatment.
• metal ions such as nickel and heavy metal ions (Hg, Cr and Pb) from the liquid under treatment.
• Hg, Cr and Pb nickel and heavy metal ions
• electrocoagulation unit may be used to reduce the chemical oxygen demand (COD) , biological oxygen demand (BOD) and/or concentration of suspended solids (TSS) in the liquid under treatment .
• COD chemical oxygen demand
• BOD biological oxygen demand
• TSS suspended solids
• the electrochemical apparatus may include a control unit containing a single source of direct current, said source being connected to the cathode and anode (s) to effect electrocoagulation, or the protective electrode and the cathode and/or anode (s) in the chamber to effect protection.
• the electrochemical apparatus may include a control unit containing a single source of direct current, said source being connected to the cathode and anode (s) to effect electrocoagulation, or the protective electrode and the cathode and/or anode (s) in the chamber to effect protection.
• the electrochemical apparatus may include a control unit containing a single source of direct current, said source being connected to the cathode and anode (s) to effect electrocoagulation, or the protective electrode and the cathode and/or anode (s) in the chamber to effect protection.
• control unit containing a source of direct current that is connected to the cathode (s) and anode (s) to effect electrocoagulation and a second source of direct current that is connected to the protective electrode and the cathode (s) and/or anode (s) in the chamber to effect protection.
• the electrochemical apparatus is an electrocoagulation unit described in WO 2008/009973.
• This electrocoagulation unit comprises an electrode chamber, which in use, has a top and a bottom, the chamber having a fluid inlet at or towards its bottom and being in fluid
• an electrode module removable through the top of the electrode chamber and including a support body supporting a plurality of electrodes, the electrode chamber and the
• Figure 1 depicts an electrocoagulation unit comprising an electrochemical chamber having an inlet (5) and an outlet (2) .
• An anodic buss bar (3) and a cathodic buss bar (4) are
• the electrocoagulation unit also comprises a protective electrode (1) and a control unit (6) , which contains a single source of direct current.
• a liquid requiring treatment is introduced into the chamber via the inlet (5) .
• the anodic buss bar (3) is connected to the cathodic buss bar (4) via the control unit (6) . This causes the consumable surfaces of the anodes to dissolve in the liquid and generate a floe.
• the treated liquid may then be removed via the outlet (2) for further purification, for example, by filtration.
• the anodes or cathodes in the chamber may be protected from corrosion by connecting the anodic buss bar (3) or cathodic buss bar (4) to the protective electrode (1) via the control unit (6) .
• This causes electrons to flow from the protective electrode (1) to the cathodes or anodes in the chamber, protecting them from corrosion .
• Control columns present the loss of electrode mass (as iron (Fe) ) which is expressed in micrograms (ug) lost per unit electrode area (cm 2 ) per hour alongside the current density, J, employed up to the respective sampling time (T xxx ) which is expressed in micro ampere (uA) per unit electrode area (cm 2 ) .
• Table 1 Summary of experimental results and settings of experiment on electrocoagulation electrodes.
• electrocoagulation as it provides an electrochemical, in situ, mechanism for electrode cleaning.
• Table 2 summarises the current densities employed during testing whilst Figure 2 presents the samples collected at each current density (Samples 1 to 5 shown from left to right) . An amount of settled floe can be seen at the bottom of each jar.

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• 2010
  • 2010-10-20 GB GB1017725.1A patent/GB2484699B/en not_active Expired - Fee Related
• 2011
  • 2011-10-20 US US13/880,603 patent/US9145312B2/en not_active Expired - Fee Related
  • 2011-10-20 WO PCT/GB2011/052034 patent/WO2012052767A1/en active Application Filing
  • 2011-10-20 EP EP11776831.7A patent/EP2630090A1/de not_active Withdrawn

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